粘性碎屑流坡面运移动力过程研究

Viscous debris flow composed of inviscid coarse particle and of viscous mud-the mixture of fine soil and water, is comment motion forms of landslide-collapse disaster along slope and has the characteristic of migration concentrated, large impact force and serious destruction. The motion process of viscous debris flow is complex and weak link of the study of landslide-collapse disaster. The influence problems of viscous mud to the motion form, migration velocity, impact force and the disaster area are worth discussed and thorough, systematic studied. This project will carry out analysis the motion mechanical mechanism, the energy dissipation mechanism, determine the key factors affecting the motion process from microscopic based on field investigation of viscous debris flow disasters, and set up dynamics relationship of adhesion force with water content of mud, shear / tensile rate and separation distance through system mechanical experiment of viscous mud, build up kinetic model and numerical model of viscous debris flow, investigate the effects about the mechanical properties of viscous mud to the movement patterns, speed, impact force and moving scope through numerical model and physical model experiment of viscous debris flow, build up quantization relation about the macro representation of the viscous debris flow movement process along slope with the viscous mud characteristics obtained from the experimental. The significance of this research make up the deficiency of the motion process study of landslide-collapse disaster, deepen the basic theory research content of landslide-collapse disasters, provides scientific basis for project layout and the design of collapse-landslide disaster prevention and control engineering.

粘性碎屑流由无粘粗颗粒和细颗粒土水混合粘性泥浆组成，是崩滑灾害常见坡面运移形式，具有运移集中，冲击力大、破坏严重等特征，其运动过程极其复杂，是崩滑灾害研究的薄弱环节。泥浆对粘性碎屑流运动形态、速度和冲击力、致灾范围的影响如何，亟待开展深入、系统的研究。本项目通过现场调查，从细观角度分析其动力学机制和内部耗能机制，确定泥浆作用下影响运动过程关键因子；通过泥浆力学实验，构建泥浆粘连力与含水率、剪切/拉伸速率、间距间动态关系式，据此构建粘性碎屑流动力学模型；构建数值模型，开展不同泥浆情况下粘性碎屑流坡面运动数值与物理模型实验，探讨泥浆对粘性碎屑流宏观表象（运动形态、速度、冲击力、范围）的影响；根据泥浆实验结果，建立泥浆特性与粘性碎屑流坡面运移宏观表象间量化关系式。本研究的意义在于弥补在崩滑灾害运移过程方面的不足，深化崩滑灾害运动过程理论研究内容，为崩滑灾害防治工程布局、设计提供科学依据。

由泥浆粗颗粒组成的粘性碎屑流运动过程复杂，泥浆特性与其运移致灾过程密切相关。本项目在崩滑灾害调查基础上，根据其物质组成和运动中粗颗粒与泥浆相互作用过程，明确粘性碎屑流运动的颗粒碰撞和泥浆粘连力学机，确定泥浆法向粘连强度、动力粘度及切向粘连强度、动力粘度为影响其运动的关键因子。以成都粘土泥浆为对象，开展旋转剪切实验，分析含水量对泥浆初剪、复剪应力峰值及灵敏度的影响。建立初剪、复剪峰值应力与含水量关系模型。确定影响泥浆剪切过程、剪切应力变化、剪应力峰值和灵敏度的含水量阈值。确定泥浆切应力与剪切速率关系数学模型。确定成都粘土泥浆流动指数并建立动力粘度归一化模型。开展以南阳膨胀土为基本物质组成的崩滑土体直剪试验、三轴试验，分析含水量、物质组成等要素对其抗剪强度、内摩擦角、粘聚力的影响。开展粘性碎屑流坡面实验，证实：（a）随泥浆密度增大，运动形态由无粘碎屑流运动逐渐向粘性碎屑流运动到整体块状运动转变；（b）粘性碎屑流坡面横向宽度、纵向运移距离和运动速率随泥浆密度的增加而减小；（c）粘性碎屑坡面具有分类现象。开展不同坡度、含水量、组成等要素的粘性碎屑流水槽试验，初步分析相关要素对堆积厚度、运移距离、宽度及速度的影响。基于PFC3D离散元法，利用泥浆试验结果设置数值模型参数，开展与黏性碎屑坡面流物理模型试验同尺寸数值模型试验，对比分析粘性碎屑流物理模型试验与数值模拟结果，证实基于PFC3D离散元法能很好的再现粘性碎屑坡面运动全过程。根据粘性碎屑流数值模型试验，将其运动过程划分为启动、加速运移和堆积三阶段，分析各阶段粗颗粒运移动力学特征，证实粗颗粒泥浆混合体坡面运动的宏观形态变化细观运动力学参数变化联系紧密，运动过程中粗颗粒间平均接触力越大，颗粒运动速率的波动频率越高，波动幅度越低；越小，波动频率低，幅度大。本研究深化崩滑灾害运动过程研究内容，成果可为崩滑灾害防治工程布局、设计提供参考。